Precision torque screwdriver

Abstract

A rotary power tool may include a main housing, a motor positioned within the main housing, a handle extending from the main housing, a trigger that is configured to activate the motor when depressed, and a control board disposed within the handle and including a microcontroller (MCU), a first Hall sensor, and a second Hall sensor. The trigger includes a trigger body, a holder fixed to the main housing, the trigger body being movable relative to the holder along a longitudinal axis, an arm fixed to the trigger body and having a magnet holder that receives a magnet, and a spring for biasing the trigger body away from the holder. The first Hall sensor and the second Hall sensor are configured to detect depression of the trigger and emit signals to the MCU for controlling operation of the motor.

What is claimed is: 
     
         1 . A rotary power tool comprising:
 a main housing;   a motor positioned within the main housing;   a handle extending from the main housing;   a trigger that is configured to activate the motor when depressed, the trigger including:
 a trigger body, 
 a holder fixed to the main housing, the trigger body being movable relative to the holder along a longitudinal axis, 
 an arm fixed to the trigger body and having a magnet holder that receives a magnet, and 
 a spring for biasing the trigger body away from the holder; and 
   a control board disposed within the handle and including a microcontroller (MCU), a first Hall sensor, and a second Hall sensor,   wherein the first Hall sensor and the second Hall sensor are configured to detect depression of the trigger and emit signals to the MCU for controlling operation of the motor.   
     
     
         2 . The rotary power tool of  claim 1 , wherein the control board is a control printed circuit board (PCB) and the power tool further includes a power printed circuit board (PCB) disposed within the handle and including switch field effect transistors (FETs) and motor FETs. 
     
     
         3 . The rotary power tool of  claim 2 , wherein the control PCB and the power PCB are in a stacked arrangement, such that the control PCB and the power PCB are parallel to each other. 
     
     
         4 . The rotary power tool of  claim 3 , wherein the switch FETs and the motor FETs of the power PCB are in facing relationship to the MCU of the control PCB. 
     
     
         5 . The rotary power tool of  claim 2 , wherein the control PCB detects depression of the trigger and, in response, controls the switch FETs and the motor FETs of the power PCB to drive the motor. 
     
     
         6 . The rotary power tool of  claim 1 , wherein the first and second Hall sensors output a logic low signal when the trigger body is depressed and the magnet passes over the first and second Hall sensors, and wherein the first and second Hall sensors output a logic high signal when the trigger body is released and the magnet is spaced away from the first and second Hall sensors. 
     
     
         7 . The rotary power tool of  claim 6 , wherein the first Hall sensor provides the logic low signal and the logic high signal to a first input of a NOR gate and to the MCU, and wherein the second Hall sensor provides the logic low signal and the logic high signal to a second input of the NOR gate and to the MCU. 
     
     
         8 . The rotary power tool of  claim 7 , wherein the NOR gate provides a logic high signal to an AND gate only when both the first and second inputs of the NOR gate receive a logic low signal, and wherein the MCU provides a logic high signal to the AND gate when the first and second Hall sensors output a logic low signal. 
     
     
         9 . The rotary power tool of  claim 8 , wherein the AND gate includes a first input receiving a signal from the NOR gate and a second input receiving a signal from the MCU, wherein the AND gate outputs a logic high signal when both the NOR gate and the MCU output the logic high signals to respective inputs of the AND gate, thereby activating the motor. 
     
     
         10 . The rotary power tool of  claim 1 , wherein an output of the first Hall sensor and an output of the second Hall sensor are the same, except that the second Hall sensor detects the presence of the magnet longer than the first Hall sensor. 
     
     
         11 . The rotary power tool of  claim 1 , wherein the trigger is a contactless trigger. 
     
     
         12 . The rotary power tool of  claim 1 , wherein the arm is fixed to and moves in unison with the trigger body. 
     
     
         13 . The rotary power tool of  claim 1 , wherein the trigger body includes guide channels that slide within guides of the holder to ensure that the trigger body travels along the longitudinal axis. 
     
     
         14 . A rotary power tool comprising:
 a main housing;   a motor positioned within the main housing;   a handle extending from the main housing;   a contactless trigger including a magnet; and   a control board disposed within the handle and including a microcontroller (MCU), a first Hall sensor, and a second Hall sensor;   wherein in response to the magnet passing over the first Hall sensor and the second Hall sensor in sequence, the MCU is configured to activate the motor.   
     
     
         15 . The rotary power tool of  claim 14 , further comprising a power board that is also disposed within the handle and is in a stacked arrangement with the control board, such that the control board and the power board are parallel to each other. 
     
     
         16 . The rotary power tool of  claim 15 , wherein power board includes switch field effect transistors (FETs) and motor FETs that are in facing relationship to the MCU of the control board, wherein output signals of the first and second Hall sensors are relayed to the switch FETs and the motor FETs to activate the motor. 
     
     
         17 . The rotary power tool of  claim 14 , wherein an output of the first Hall sensor and an output of the second Hall sensor are the same, except that the second Hall sensor detects the presence of the magnet longer than the first Hall sensor. 
     
     
         18 . The rotary power tool of  claim 14 , wherein the trigger moves along a longitudinal axis when depressed. 
     
     
         19 . The rotary power tool of  claim 18 , wherein the first Hall sensor and the second Hall sensor are disposed adjacent to each other sequentially in a direction parallel to the longitudinal axis. 
     
     
         20 . The rotary power tool of  claim 18 , wherein the contactless trigger includes guide channels that slide within guides of a trigger holder to ensure that the contactless trigger travels along the longitudinal axis.